New 'Consciousness Meter' Could Aid Brain-Injury Treatments

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A new technique that can determine a person's level of
consciousness could benefit patients who have suffered brain
damage. These patients range from those who are fully aware but
are unable to respond — known as "locked-in syndrome" — to those
in a vegetative state, oblivious to the world.

The technique, which entails sending a magnetic pulse across the
brain and measuring the brain's response to it, has the
potential to measure consciousness even when the patient
cannot reply to other stimuli, such as light, sound or hand
squeezing.

The scientists involved in the development of this technique
caution that it shouldn't be used to determine whether to "pull
the plug" on someone in a
vegetative state. Rather, they said, the technique could be
used to monitor a patient's day-to-day recovery following a brain
injury, and to determine whether the patient is thinking or
feeling anything.

A description of the technique, called the Perturbational
Complexity Index (PCI), appears today (Aug. 14) in the journal
Science Translational Medicine.

Is there anybody in there?

The
nature of consciousness has long been elusive, debated by
scientists and philosophers alike. People routinely enter an
unconscious state when they're in a deep sleep or under
anesthesia, but ultimately, they awaken.

Yet a person's appearance does not always yield clues to their
consciousness — those who have suffered severe brain injuries may
be fully conscious, or awake, yet they simply appear unconscious
due to their inability to move or respond to stimuli. Conversely,
those in a vegetative state can perceive nothing of the world
around them, yet they might appear conscious, occasionally
moving, grimacing and even groaning. [ 10
Ways to Keep Your Mind Sharp ]

The new research, led by Dr. Marcello Massimini at the University
of Milan in Italy, started with the theoretical idea that
consciousness depends on the brain's ability to coordinate
information across interacting regions. A magnetic pulse sent
through these regions should stimulate the brain, and produce a
specific activity pattern that could be measured by
electroencephalography (EEG).

Earlier work by these researchers showed a pulse in a conscious
brain produced a rich, full EEG signal across the entire brain.
In contrast, a pulse in an unconscious brain, in deep sleep or
under anesthesia, produced a shorter, stunted EEG signal.

To sleep, perchance to dream

The new study expanded this test to 52 people in various states
of consciousness and unconsciousness: wakefulness, a light
stage
of sleep called dream sleep, deep sleep, sedation induced by
different types of anesthesia, a coma-induced minimally conscious
state, locked-in syndrome and a vegetative state (now called
"unresponsive wakefulness syndrome").

Those who were anesthetized had PCIs as low as 0.12, which means
they were in a deep state of unconsciousness. The more potent the
anesthesia, the lower the PCI.

Among patients with brain damage, those thought to be in a
vegetative state had PCIs similar to people deeply under
anesthesia. The patients suffering from locked-in syndrome were
wide-awake, with PCIs of about 0.6, and those in a minimally
conscious state had PCIs of about 0.3.

Massimini said he would like to expand the study to more patients
in order to better define the index. Tens of thousands of
Americans have severe brain damage, according to various
published estimates. These include many soldiers and veterans who
fought in Iraq and Afghanistan.

"An important potential application of PCI is to monitor the
effect of treatments," Massimini told LiveScience. "The efficacy
of drugs or brain-stimulation procedures may be judged
objectively and quantitatively based on their effects on brain
complexity."

However, Massimini said the PCI can't be used to determine
absolute unconsciousness.

"No objective measure can be used to rule out the presence of
consciousness, because we do not have a clear understanding of
what are the physical properties that are necessary and
sufficient for subjective experience," he said. "When measuring
consciousness, it is safe to say that the absence of the proof is
not proof of the absence."

Christopher Wanjek is the author of a new novel, " Hey,
Einstein! ", a comical nature-versus-nurture tale about
raising clones of Albert Einstein in less-than-ideal settings.
His column, Bad Medicine,
appears regularly on LiveScience.